Birefringent stretched films have conventionally been used as retardation films used for eliminating phase difference in liquid crystal display devices, but recently, optically anisotropic media prepared by applying a polymerizable liquid crystal to a substrate provided with an alignment film and subsequently curing the liquid crystal molecules while in an aligned state have been developed as retardation films with more complex optical properties (for example, see Patent Document 1). These media are obtained by providing a polymer film of a polyimide or the like on a substrate, rubbing this polymer film in a single direction with a cloth or the like to generate an aligned film, applying a polymerizable liquid crystal to the surface of the film, thereby aligning the liquid crystal molecules with the rubbing direction, and then polymerizing the liquid crystal to fix the alignment, and by appropriate combination of the alignment direction of the alignment film and the state of alignment of the polymerizable liquid crystal, a retardation film can be obtained that has optical properties unattainable using a stretched birefringent film.
Recently, optical compensation sheets having excellent durability have also been developed by rubbing a polyimide coating film having a polymerizable group provided on top of a substrate, applying a discotic liquid crystal having a polymerizable group to the coating film, and chemically bonding the polyimide alignment film and the optically anisotropic layer of the discotic liquid crystal at the interface therebetween (for example, see Patent Document 2).
However, because the optical compensation sheet disclosed in Patent Document 2 uses a rubbed alignment film, scratches and dust generated during the rubbing can be problematic. Generated dust can be removed by washing or the like, but scratches cannot be removed, meaning there is a possibility of a significant deterioration in the optical uniformity of the laminated liquid crystal film.
On the other hand, optically anisotropic media in which a layer (A) that has been imparted with a liquid crystal alignment ability by irradiation with light, and a polymer layer (B) obtained by polymerizing a liquid crystal compound having a polymerizable group in an aligned state generated by the layer (A) are bonded and laminated together via covalent bonding have also been developed (for example, see Patent Document 3). Because these optically anisotropic media use a photo-alignment film, scratches and dust are not generated during production. Furthermore, because the layer (A) having a liquid crystal alignment ability and the polymer layer (B) are reacted together at the interface therebetween, the bonding at the interface is excellent, and an optically anisotropic medium of superior durability can be obtained.
However, with the optically anisotropic medium disclosed in Patent Document 3, if a plastic substrate such as a TAC film or PET film is used as the substrate, then peeling or the like may sometimes occur.    [Patent Document 1]    Japanese Unexamined Patent Application, First Publication No. Hei 5-215921    [Patent Document 2]    Japanese Unexamined Patent Application, First Publication No. 2001-89657    [Patent Document 3]    Japanese Unexamined Patent Application, First Publication No. 2005-173548